Ditto for the comments on DL having no real one way awards. Also for the suggestion to consider purchasing the domestic segments if they cause the number of miles required to increase.

I'm not sure it makes sense to spend money now when you won't be issuing reward tickets for so many months. By then, the miles required could go up much higher and you still won't be able to get your SYD tickets or nothing at all could be available for the date range you want.